arc: Implement new UI for general ARC ghost window

This CL implement new UI of ARC ghost window.

(1) App icon shadow
(2) New layout
(3) Dark mode support

BUG=b:249474491
BUG=b:255486588
TEST=manually check

Change-Id: I6f28a1649cf733931c9c6bc33d3c27cb4762a5a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3986684


Reviewed-by: Yuichiro Hanada <yhanada@chromium.org>
Commit-Queue: Shengsong Tan <sstan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1064791}